{"id":6415,"date":"2023-01-13T02:09:21","date_gmt":"2023-01-13T02:09:21","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=6415"},"modified":"2023-01-13T02:20:29","modified_gmt":"2023-01-13T02:20:29","slug":"django-order_by","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/django-tutorial\/django-order_by\/","title":{"rendered":"Django order_by"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use Django order_by<\/code> to sort rows by one or more columns in ascending or descending order.<\/p>\n\n\n\n

Introduction to the Django order_by() method #<\/a><\/h2>\n\n\n\n

When defining a model<\/a>, you can specify the default order of the results returned by a QuerySet<\/code> by using the ordering<\/code> option in the model’s Meta<\/code> class.<\/p>\n\n\n\n

We’ll use the Employee model for the demonstration. The Employee model maps to the hr_employee table in the database:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

For example, to sort the employee by first and last names alphabetically, you can specify the first_name<\/code> and last_name<\/code> fields the ordering<\/code> option in the Meta<\/code> class as follows:<\/p>\n\n\n

class<\/span> Employee<\/span>(models.Model)<\/span>:<\/span>\n<\/span><\/span>    # ...<\/span>\n<\/span><\/span>\n<\/span><\/span>    class<\/span> Meta<\/span>:<\/span>\n<\/span><\/span>        ordering = ['first_name'<\/span>, 'last_name'<\/span>]\n<\/span><\/mark><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
To sort the values in descending order, you add the -<\/code> character in front of the field name. For example, the following uses the ordering<\/code> option to sort the employees by first name in descending order and last name in ascending order:<\/p>\n\n\n
class<\/span> Employee<\/span>(models.Model)<\/span>:<\/span>\n<\/span><\/span>    # ...<\/span>\n<\/span><\/span>\n<\/span><\/span>    class<\/span> Meta<\/span>:<\/span>\n<\/span><\/span>        ordering = ['-first_name'<\/span>, 'last_name'<\/span>]\n<\/span><\/mark><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Also, you can use a query expression to make null values appear first or last in the sorted result:<\/p>\n\n\n
from<\/span> django.db.models import<\/span> F\n<\/span><\/span>\n<\/span><\/span>class<\/span> Employee<\/span>(models.Model)<\/span>:<\/span>\n<\/span><\/span>    # ...<\/span>\n<\/span><\/span>\n<\/span><\/span>    class<\/span> Meta<\/span>:<\/span>\n<\/span><\/span>        ordering = [F('first_name'<\/span>).asc(nulls_last=True<\/span>)]\n<\/span><\/mark><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
To override the default sort order, you use the order_by()<\/code> method of a QuerySet<\/code>:<\/p>\n\n\n
order_by(*fields)<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The following example uses the order_by()<\/code> to sort employees by first name in ascending order:<\/p>\n\n\n
>>> <\/span>Employee.objects.all().order_by('first_name'<\/span>)             \n<\/span><\/mark>SELECT \"hr_employee\"<\/span>.\"id\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"first_name\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"last_name\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"contact_id\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"department_id\"<\/span>\n<\/span><\/span>  FROM \"hr_employee\"<\/span>\n<\/span><\/span> ORDER BY \"hr_employee\"<\/span>.\"first_name\"<\/span> ASC\n<\/span><\/mark> LIMIT 21<\/span>\n<\/span><\/span>Execution time: 0.001034<\/span>s [Database: default]\n<\/span><\/span><QuerySet [<Employee: Aaron Pearson>, <Employee: Adam Crane>, <Employee: Adam Stewart>, <Employee: Adrienne Green>, <Employee: Alan Johnson>, <Employee: Alexa West>, <Employee: Alicia Wyatt>, <Employee: Amanda Benson>, <Employee: Amber Brown>, <Employee: Amy Lopez>, <Employee: Amy Lee>, <Employee: Andre Perez>, <Employee: \n<\/span><\/span>Andrea Mcintosh>, <Employee: Andrew Guerra>, <Employee: Andrew Dixon>, <Employee: Ann Chang>, <Employee: Anne Odom>, <Employee: Anthony Welch>, <Employee: Anthony Fuentes>, <Employee: Ashley Brown>, '...(remaining elements truncated)...'<\/span>]>\n<\/span><\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Like the ordering<\/code> option, you can use the order_by()<\/code> method to sort the employee by the first name in descending order:<\/p>\n\n\n
>>> <\/span>Employee.objects.all().order_by('-first_name'<\/span>) \n<\/span><\/mark>SELECT \"hr_employee\"<\/span>.\"id\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"first_name\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"last_name\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"contact_id\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"department_id\"<\/span>\n<\/span><\/span>  FROM \"hr_employee\"<\/span>\n<\/span><\/span> ORDER BY \"hr_employee\"<\/span>.\"first_name\"<\/span> DESC\n<\/span><\/mark> LIMIT 21<\/span>\n<\/span><\/span>Execution time: 0.000998<\/span>s [Database: default]\n<\/span><\/span><QuerySet [<Employee: William Wise>, <Employee: Wendy Reilly>, <Employee: Victoria Forbes>, <Employee: Victoria Schneider>, <Employee: Vicki Baker>, <Employee: Veronica Blackburn>, <Employee: Vanessa Allen>, <Employee: Valerie Nguyen>, <Employee: Tyler Coleman>, <Employee: Tyler Briggs>, <Employee: Troy Ashley>, <Employee: Travis Goodwin>, <Employee: Tony Jordan>, <Employee: Todd Evans>, <Employee: Timothy Dillon>, <Employee: Timothy Mckay>, <Employee: Timothy Williams>, <Employee: Timothy Lewis>, <Employee: Tiffany Holt>, <Employee: Tiffany Jackson>, '...(remaining elements truncated)...'<\/span>]>\n<\/span><\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The order_by()<\/code><\/code> also allows you to sort the results by multiple fields. For example, the following uses the order_by()<\/code><\/code> to sort employees by first and last name:<\/p>\n\n\n
>>> <\/span>Employee.objects.all().order_by('first_name'<\/span>,'last_name'<\/span>)\n<\/span><\/mark>SELECT \"hr_employee\"<\/span>.\"id\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"first_name\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"last_name\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"contact_id\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"department_id\"<\/span>\n<\/span><\/span>  FROM \"hr_employee\"<\/span>\n<\/span><\/span> ORDER BY \"hr_employee\"<\/span>.\"first_name\"<\/span> ASC,\n<\/span><\/mark>          \"hr_employee\"<\/span>.\"last_name\"<\/span> ASC\n<\/span><\/mark> LIMIT 21<\/span>\n<\/span><\/span>Execution time: 0.000998<\/span>s [Database: default]\n<\/span><\/span><QuerySet [<Employee: Aaron Pearson>, <Employee: Adam Crane>, <Employee: Adam Stewart>, <Employee: Adrienne Green>, <Employee: Alan Johnson>, <Employee: Alexa West>, <Employee: Alicia Wyatt>, <Employee: Amanda Benson>, <Employee: Amber Brown>, <Employee: Amy Lee>, <Employee: Amy Lopez>, <Employee: Andre Perez>, <Employee: \n<\/span><\/span>Andrea Mcintosh>, <Employee: Andrew Dixon>, <Employee: Andrew Guerra>, <Employee: Ann Chang>, <Employee: Anne Odom>, <Employee: Anthony Fuentes>, <Employee: Anthony Welch>, <Employee: Ashley Brown>, '...(remaining elements truncated)...'<\/span>]>\n<\/span><\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
To order randomly, you can use a question mark ?<\/code> like this:<\/p>\n\n\n
>>> <\/span>Employee.objects.all().order_by('?'<\/span>)                      \n<\/span><\/mark>SELECT \"hr_employee\"<\/span>.\"id\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"first_name\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"last_name\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"contact_id\"<\/span>,\n<\/span><\/span>       \"hr_employee\"<\/span>.\"department_id\"<\/span>\n<\/span><\/span>  FROM \"hr_employee\"<\/span>\n<\/span><\/span> ORDER BY RANDOM() ASC\n<\/span><\/mark> LIMIT 21<\/span>\n<\/span><\/span>Execution time: 0.010370<\/span>s [Database: default]\n<\/span><\/span><QuerySet [<Employee: Daniel Meyer>, <Employee: Todd Evans>, <Employee: Roger Robinson>, <Employee: Dwayne Williams>, <Employee: Michael Murphy>, <Employee: Daniel Friedman>, <Employee: Claudia Aguilar>, <Employee: Craig Hunter>, <Employee: Amanda Benson>, <Employee: Renee Wright>, <Employee: Wendy Reilly>, <Employee: Jamie Jackson>, <Employee: Philip Jones>, <Employee: Kelly Stewart>, <Employee: Barbara Vincent>, <Employee: Drew Gonzalez>, <Employee: Derek Owens>, <Employee: Lauren Mcdonald>, <Employee: Perry Rodriguez>, <Employee: Matthew Hernandez>, '...(remaining elements truncated)...'<\/span>]>\n<\/span><\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
The order_by<\/code>(‘?’) maybe slow and expensive, depending on the database that you’re using. The above-generated SQL<\/code> is from PostgreSQL. Other databases may have different implementations.<\/p>\n\n\n\n